I have a question about FCC part 15 certs. Using the Particle Cellular B series SoM, they have a "Grant of equipment authorization" to use the module as an end device. Link to the module docs below.

Within the terms, it says you must use the same type of antenna and less than or equal to the gain that it was certified with.

My question is, if I use an extension cable, say to get it outside a machine for better signal, does this violate the FCC cert? I do not want to pay for re-certification. The docs don't really say anything about this.

Adding cable does become part of the antenna and could affect things. So I'm not sure if this is valid or not. I'm using the same type of antenna, in fact it's the exact antenna it was certified with, but with a longer cable.

The antenna in question is the Taoglas FXUB63. It is a flat flex PCB (flat patch) antenna with a U.FL connector. So can I use a U.FL to U.FL extension cable and still be within the Grant of equipment authorization? Or maybe even a U.FL to SMA and an long SMA extension and then back to U.FL. You get the idea.

You can find the FCC certification docs here: https://docs.particle.io/datasheets/certifications/certification/

Antenna: https://www.digikey.com/product-detail/en/taoglas-limited/FXUB63.07.0150C/931-1329-ND/4965532


2 Answers 2


The short answer is that should be fine.

I have not seen the FCC specifically address this exact question but I think it is fair to say you can infer their answer from their published guidance on permissive antenna changes.

In this document they talk about what type of antenna substitutions you can make without filing for a Class II permissive change. With an extension cable you are reducing the gain of the system but the antenna type is not changing and you should not otherwise be altering the in-band and out-of-band characteristics.

You will still have to do FCC Part 15B unintentional radiator testing for the whole system the SOM plugs into (assuming you have at least some switching components on the carrier board for the SoM).

You probably won't find a u.FL to u.FL adapter cable, but you can find a u.FL to SMA adapters.

You would still probably be better off just using their antenna builder and just getting the cable length you want.


usually, if the board has an RF connector, FCC measurements are taken by connecting the RF connector to an EMI receiver by a coaxial cable.

In words: RF measurements are conducted measurements.

They measure the maximum/peak/average power coming out from the RF connector.

That gives the end user the maximum flexibility when choosing an external antenna or cable+antenna.


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